The environment a party finds themselves in can be an adventure in its own right. With the proper application and imagination, any environment can be turned into a character all its own. From the high seas to deep underground, from the darkest jungle to an active volcano, the environment an adventure or encounter takes place in can alter the entire mood.
I'd like to state that when it comes to setting, a high-magic game like D&D and Pathfinder may have difficulty being challenged by an environment. Spells like create food and water and endure elements make most hazards obsolete. They tend to work better for low-magic games, where it is difficult to cast spells, and choosing to do so can be resource costly. However, this shouldn't discourage a DM from putting them in regardless. Each spell slot used for survival is a slot not used for some other spell that they may need. It is still a choice.
Let's address some particular environments and some potential ideas for making them interesting.
Desert: The endless burning sands are one of the most dangerous terrains available. Intense heat during the day, freezing cold at night, little food, no water, and let's not forget the threat of stinging sandstorms. Any location is only as dangerous as the DM makes it, and forgetting to apply these threats effectively makes the desert no different than a grassy plain. As the party trudges through the endless sand dunes, make sure to describe the intense heat, causing burning damage to them. Players in metal armor will find it unbearable, forcing them to remove it. Tell them how their hunger and thirst causes them to see images in the distance, and how lack of food is weakening them. At night, describe the icy coldness, as bad as a glacier, threatening to freeze them. Then in the morning or sunset, when things are their most ideal, a sudden sand storm picks up. They must find cover or die, and if they try to make progress in it, how the dunes have changed, are we sure we are going the right direction? The desert is an unforgiving nightmare. Let your players experience it in all its awesome power.
Jungle: Where deserts suffer from a lack of flora and fauna, jungles could be said to suffer from an overabundance. The jungle's primary danger is the creatures and plants that reside within it. But we can discuss monsters any day, let's talk about the plants. Now by plants I don't mean monster plants with combat stats, I mean things like molds, fungi, spores, and natural every day dangers of the jungle. The jungle's humidity allows for a number of plants to grow, providing a constant bombardment of poisons and diseases that will test the party's Fortitude saves to the max. There are several resources online that can detail a number of deadly plants ready for use, and the best part is that they can be used in almost any setting. Getting lost is also a problem, as the foliage makes it hard to see in the distance, and the noises of animals can make it hard to maintain bearings. In my mind, jungles, and by extension rainforests, are always filled with poison. Everything is poisonous, and everything can kill you in seconds.
Volcanic: Lava is a pretty big danger all on its own. Not much needs to be said about lava that you don't already know. It's bad. Don't touch it. But some people may not know that even getting anywhere near lava is deadly. Lava is so hot, you can burn your lungs just breathing the air that's been heated from being in contact with it. I usually start the burning damage that accompanies natural heat as close as forty feet from lava, while a more intense searing heat happens at twenty feet. If I'm feeling particularly cruel, I might make damage caused by contact with magma be permanent, or at least require a miracle, wish, or greater restoration to repair. No matter what the circumstance, lava is bad, and the rules don't read that it is much worse than fire, so I add my own particular dangers to it. Aside from magma however, a volcanic setting can also have dangerous crags and sharp jutting rocks that are painful to walk on. Players without metal boots may take damage, and even those with may find the sharp rocks quickly sundering through them.
Sea: The seas, both above and below them, carry their fair share of problems. Lack of fresh water, drowning, tidal waves, undersea currents, storms, and the eternal danger of being irretrievably lost. Drowning is actually quite hard to do in RPG games, as most players are more than aware of their exact limit on breath and will usually not tempt fate. However, if a monster knocks them unconscious and then tosses them overboard, the danger suddenly becomes much more real, especially if they are wearing their armor. Armor is an interesting double-edged sword on the sea. Wearing it helps if you're attacked, but fall overboard and it is suddenly your worst enemy. With all the monsters in the sea, the storms, the currents, a player may find armor is simply too much a risk to wear. For long voyages that go awry, I like to calculate exactly how much food may be available, and then see how fast I can give everyone scurvy. When describing a sea voyage, if the adventure itself isn't the voyage there, then I find there isn't much reason to delay a trip longer than a simple fight or two.
Arctic: The freezing cold of the high north and the low south bring with it more dangers than may be readily apparent. Ice is cold yes, and that is a real threat to a party ill-prepared, but the same problems I've mentioned before arise. Little to no food, changing landmarks, cloudy skies that reveal nothing of bearings, unstable ice floes that may either break as they walk upon them, or break off to separate floating masses, perhaps splitting the party. Though water may be plentiful, can a party use heat to warm water when they must use all there is to keep themselves warm? The arctic makes for a unique environment to have an adventure, and one I have had fun using in my own games.
Underground: The underground is perhaps the most commonly used of environments in D&D and Pathfinder, if sadly the most underutilized. The magic of the underground is that it can contain the dangers of any of the previously mentioned environments. Heat, cold, starvation, thirst, drowning, suffocation, humidity, spores, molds, fungi, getting lost, and yes, even storms. Nothing and no one is safe underground, but usually any particular area is singularly focused on a hazard, and rarely does one see layered death traps. Still, this particular template remains the most open to interpretation.
Finally, I find that a detailed description of an environment, coupled with interesting and varied encounters, can really add flavor to an adventure. The location should never merely be a backdrop, but I feel should be brought to the forefront, where it can shine as a character in its own right, relentlessly attacking the party at every turn. Thanks for reading, stay tuned tomorrow for "F is for Familiar".